Aerial vehicles and control therefor

ABSTRACT

A method for turning an aerial vehicle such as a drone-type vehicle is provided, according to one embodiment. The method provides for receiving a turning input and detecting a current momentum of the aerial vehicle. The method provides for converting the turning input into a yaw command and calculating a change in yaw associated with the turning input. The method provides for calculating a roll command based on the current momentum of the aerial vehicle and based on the change in yaw associated with the turning input. Further, the method provides for executing the yaw command and the roll command in synchrony, wherein the executing the yaw command and the roll command in synchrony causes the aerial vehicle to perform a turn.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/942,421, entitled “AERIAL VEHICLES AND CONTROL THEREFOR,” filed onMar. 30, 2018, the entirety of which is hereby incorporated byreference.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to manned and unmanned aerialvehicles, and more particularly to user control systems that enable auser to control a change of direction of the aerial vehicle.

BACKGROUND

Aerial vehicles such as drones and vertical and take-off and landing(VTOL) vehicles can be unintuitive to control. This is especially truefor novice pilots. The difficulties in piloting an aerial vehicle,whether manned or unmanned, stem from a number of fundamentaldifferences between the physics of an aerial vehicle and that of morefamiliar vehicles having wheels. Wheeled-vehicles, such as bicycles,cars, motor bikes, all-terrain vehicles (ATVs), scooters, hoverboards,etc., experience static friction with the ground through their wheels.Wheeled vehicles are not only propelled through contact with the groundvia static friction, but also navigate turns via static friction. Forexample, when a bicycle turns, the front wheel guides the bicycle in thedirection of the turn. As the bicycle turns, the momentum of the bicycleis aligned with the bicycle's direction (e.g., the direction the bicycleis pointed). The alignment of the bicycle's momentum with itsorientation is maintained throughout the turn. For an operator of thebicycle, such an alignment is intuitive and familiar, as the operatorcan simply “point and go” while riding the bicycle.

Aerial vehicles such as manned aerial vehicles (MAV) and unmanned aerialvehicles (UAV) must navigate: turns in a much different manner becauseof their lack of static friction with a surface. Often, MAVs may beoriented in a direction that is different that its momentum. Forexample, to have an MAV turn in a manner similar to a bicycle, the pilotmust separately rotate the vehicle (e.g., change the vehicle's yaw) andchange the vehicles momentum (e.g., change the vehicle's) at the sametime and at precise magnitudes. For many aerial vehicles, such a turnwould require input using separate input controls. In most commerciallyavailable drones, for example, a control unit may have a joystick thatcontrols altitude (e.g., thrust) and yaw and a separate joystick thatcontrols pitch and roll. Thus, in order to navigate a turn similar to awheeled vehicle where momentum and orientation/directionality arealigned, a pilot is required to precisely control a yaw input with onehand and a roll input with the other. Such a concerted input isunintuitive and difficult to learn. Further, current control and inputmethods for aerial vehicles may hamper the ability of operators tocontrol manned aerial vehicles in a familiar and comfortable manner.

It is in this context that embodiments arise.

SUMMARY

Embodiments of the present disclosure relate to methods and systems forcontrolling the behavior of an aerial vehicle (AV).

In one embodiment, a method for turning an aerial vehicle is provided.The method includes receiving, at the aerial vehicle, a turning input.The method includes detecting a current momentum of the aerial vehicle.Further, according this embodiment, the method provides for convertingthe turning input into a yaw command and calculating a change in yawassociated with the yaw input. The method also provides for calculating,in response to the turning input, a roll command based on the currentmomentum of the aerial vehicle and based on the change in yaw associatedwith the turning input. Additionally, the method provides for executing,by the aerial vehicle, the yaw command and the roll command insynchrony, wherein the executing the yaw command and the roll command insynchrony causes the aerial vehicle to perform a turn.

In another embodiment, an aerial vehicle is provided. The aerial vehicleincludes one or more sensors for determining a momentum of the aerialvehicle, a single axis turning device for receiving yaw inputs, and abody for supporting a pilot. The aerial vehicle also includes a flightcomputer for converting the yaw inputs into yaw commands, the flightcomputer includes a momentum alignment correction module for generatingroll commands operable to adjust a roll of the aerial vehicle based onthe yaw commands and based on the momentum of the aerial vehicle. Theaerial vehicle further includes a plurality of propulsion units forexecuting the yaw commands and the roll commands, the executing the yawcommands and the roll commands causes the aerial vehicle to navigate aturn.

In another embodiment, a method for controlling an aerial vehicle isprovided. The method includes receiving a yaw input from a user of theaerial vehicle and detecting a momentum of the aerial vehicle. Themethod also provides for calculating, in response to the yaw input, arate of change in yaw of the aerial vehicle based on the yaw input.Further, the method provides an operation for calculating, in responseto the yaw input, a roll command based on the yaw input and the momentumof the aerial vehicle, the calculating the roll command includesdetermining a change in a direction of the momentum required to matchthe rate of change in yaw of the aerial vehicle. Additionally, themethod provides for executing, by propeller units associated with theaerial vehicle, the change in yaw and the roll command in unison. Insome embodiments, the executing the change in yaw and the roll commandin unison causes the aerial vehicle to navigate a turn, wherein anorientation vector and a momentum vector of the aerial vehicle arealigned during the turn.

Other aspects of the disclosure will become apparent from the followingdetailed description, taken in conjunction with the accompanyingdrawings, illustrating by way of example the principles of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may best be understood by reference to the followingdescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a conceptual illustration of certain differences between how aground vehicle and how an aerial vehicle experience rotation, accordingto one embodiment.

FIGS. 2A-2D show conceptual illustrations of flight characteristics of africtionless vehicle in response to various inputs, according variousembodiments.

FIGS. 3A-3B show conceptual illustrations of how a frictionless vehiclebehaves with and without momentum alignment correction, according oneembodiment.

FIG. 4 shows a conceptual illustration how an aerial vehicle navigates aturn with momentum alignment correction (MAC) in response to a singleaxis turning input, according to one embodiment.

FIG. 5A shows a hoverbike embodiment of an aerial vehicle that may beimplemented with the MAC processes described herein, according to oneembodiment.

FIG. 5B shows a first person view of the hoverbike embodiment.

FIG. 6 shows a schematic diagram of an aerial vehicle and associatedpropulsion units, according to one embodiment.

FIG. 7 shows a simulation of how momentum alignment correction enablesan aerial vehicle to navigate an in-progress turn while maintainingalignment between its momentum vector and its directionality vectorduring the in-progress turn, according to one embodiment.

FIG. 8 shows a simulation how momentum alignment correction enables anaerial vehicle to complete a turn at a relatively lower speed whilemaintaining alignment between its momentum vector and its directionalityvector during the completed turn, according to one embodiment.

FIG. 9 shows a simulation how momentum alignment correction enables anaerial vehicle to complete a turn at a relatively higher speed whilemaintaining alignment between its momentum vector and its directionalityvector during the completed turn, according to one embodiment.

FIG. 10 shows a simulation of how momentum alignment correction enablesan aerial vehicle to perform a variable turn with course correctionwhile maintaining the aerial vehicle's momentum vector with itsdirectionality vector during the variable turn, according to oneembodiment.

FIGS. 11A and 11B show how turn inputs are mapped in real time to powerdistribution curves for supplying power to various propulsion unitsusing momentum alignment correction for a turn in progress and acompleted turn, respectively, according to various embodiments.

FIGS. 12A and 12B show how turn inputs are mapped in real time to powerdistribution curves for supplying power to various propulsion unitsusing momentum alignment correction for a completed turn at a relativelylower speed and a relatively higher speed, respectively, according tovarious embodiments.

FIG. 13A shows an overall flow of a method embodiment for executingmomentum alignment correction for turning an aerial vehicle, accordingto one embodiment.

FIG. 13B shows an embodiment of a flight computer of an aerial vehiclethat is enabled to carry out momentum alignment correction processes,according to one embodiment.

FIG. 14 shows an overall flow of a method embodiment for implementingmomentum alignment correction in an aerial vehicle that is furtherenabled to make momentum corrections in response to detectingnon-alignment between momentum and orientation of the aerial vehicle,according to one embodiment.

FIGS. 15A and 15B show embodiments of over-roll correction processes foran aerial vehicle, according to one embodiment.

FIG. 16 shows a method embodiment for implementing over-roll correctionor prevention in aerial vehicles, according one embodiment.

DETAILED DESCRIPTION

The following embodiments describe methods, computer programs, andapparatuses relate generally to controlling the flight behavior ofaerial vehicles (AVs), and more particularly to improving theintuitiveness of how an AV navigates turns. It will be obvious, however,to one skilled in the art, that the present disclosure may be practicedwithout some or all of these specific details. In other instances, wellknown process operations have not been described in detail in order tonot unnecessarily obscure the present disclosure.

Aerial vehicles, and more particularly drone-type aerial vehicles, areno intuitive to operate as ground vehicles, especially as it relatesturning. Ground vehicles such as automobiles, bicycles, motorcycles,scooters, hoverboards and the like, are more intuitive to turn becausethe turning of a ground vehicle changes the momentum vector of thevehicle to match the magnitude of the turn. Generally speaking, agrounded vehicle's momentum vector will consistently matchdirectionality vector (e.g., the vehicle faces the same direction ittravels). This change in the momentum vector is caused by anacceleration of the ground vehicle in the direction of the turn, theforce for which is provided by the static friction between the wheels ortires and the ground. As a result, the vehicle is able to “push off” ofthe points of contact between the ground vehicle and the ground to causea change in the direction of the vehicle's momentum.

Generally, there is a degree of alignment between the ground vehicle'sorientation (e.g., the direction the vehicle is facing) and its momentumvector, although it may take a period of time between the moment ofturning of a ground vehicle and the time the momentum vector “catchesup” to the direction of the turn. Such an alignment between momentum andorientation feels natural to human operators. When alignment betweenmomentum and orientation is disrupted, as may be the case when a carspins out or hydroplanes, the average human operator is at a loss forcontrolling the vehicle in this non-aligned state.

Drone-type AV's such as quadcopters are in a constant state ofnon-alignment. Conventionally speaking, an AV's momentum vector isindependent of its orientation. For example, when a north-traveling andnorth-facing AV is given a westward yaw input, the result may be awest-facing AV that is still traveling in the north-facing direction. Ifan operator wishes instead to make a full 90° turn toward the west whilealso facing the west the operator must manually decrease the AV'snorthward momentum to zero, increase the AV's westward momentum, andchange the yaw of the AV by 90°.

To navigate such a turn with considerable speed while maintainingmomentum-to-orientation alignment, as would be automatic in a groundvehicle, is extremely difficult even for more experienced operators.What is desired, therefore, are methods and systems that enable an AV,both manned and unmanned, to be able to navigate turns withmomentum-to-orientation alignment (e.g., alignment between an AV'smomentum vector and its direction vector). Embodiments described hereare for manned aerial vehicles (MAVs) and unmanned aerial vehicles(UAVs) and methods for their control that enable momentum-to-orientationaligned turning through momentum alignment correction (MAC) processes.Such embodiments are contemplated to be technological improvements uponcurrent MAVs and UAVs for their ability to automatically correct theAV's momentum vector to align with the AV's orientation, which providefor more intuitive flight characteristics as well as human-machineinterfacing. It is also contemplated that certain embodiments describedhere that implement automatic momentum alignment correction (MAC) mayalso mimic the turning characteristics and experience of ground vehiclesfor frictionless vehicles. Such mimicking is also envisioned to be atechnological improvement to the way AV's behave such that operators areprovided with familiar, intuitive, and predictable flightcharacteristics and responsiveness.

As used herein, the term “momentum vector” is used to refer to themagnitude and direction associated with an object's momentum.

As used herein, the term “directionality vector” is used to refer to thedirection in which an object such as a vehicle is facing.

As used herein, “alignment” between two vectors is used to refer tostates in which the two vectors are facing in the same direction,generally. Alignment does not necessarily refer to co-linearity orco-directionality, per se.

As used herein, “frictionless” vehicle is meant to denote a vehicle thatdoes not experience friction from the ground during normal operation,but that may, and does, experience friction in other ways, for example,by way of drag, etc.

FIG. 1 shows a conceptual illustration of certain differences betweenhow a ground vehicle and how a frictionless vehicle such as an aerialvehicle experience a change in yaw or rotation, according to oneembodiment. When bicycle 100 is traveling along a forward path prior toa turn, its momentum vector 102 and its direction vector 104 arealigned. That is, for example, the bicycle 100 faces in a direction thatcorresponds to a direction of its momentum. A frictionless vehicle 101such as a drone-type aerial vehicle is also shown to also have amomentum vector 106 that is aligned with its direction vector 108 priorto a turn, similar to the bicycle 100.

After the bicycle 100 turns toward the right, its direction vector 104′after the turn and its momentum vector 102′ after the turn are shown toboth be directed to the right. Notably, the momentum vector 102′ remainsaligned with the direction vector 104′ after the turn. Generally, mostwheeled vehicles will have a momentum that maintains alignment with itsdirectionality. Having a momentum vector that aligns with directionalityvector makes intuitive sense for an operator of a wheeled vehicle suchas bicycle 100, because human are accustomed to facing the direction inwhich they move. For example, when a human walks or runs, his or hernatural or default head position faces in the same direction that he orshe is traveling.

Current drone-type AVs are not configured to maintain a momentum vectorthat is aligned with its directionality vector. Instead, currentdrone-type AVs are configured to have a momentum component and anorientation component that are independently controlled. For example,FIG. 1 shows the momentum vector 106′ of the frictionless vehicle 101 tono longer be aligned with the direction vector 108′ of the frictionlessvehicle 101 after the turn. In particular, the direction 108′ is shownto be facing toward the right after the turn, while the momentum vector106′ still faces the same direction as momentum vector 106 prior to theturn. This may occur, for example, if an operator of the frictionless101 provides a yaw input alone. As a result, the direction vector 108′of the frictionless vehicle 101 without affecting the momentum vector106′ in current AVs. The result is a frictionless vehicle 101 that doesnot travel in the same direction that it faces.

FIGS. 2A-2D show conceptual illustrations of flight characteristics offrictionless vehicles in response to various inputs, according variousembodiments. FIG. 2A shows a scenario in which a frictionless vehicle101-1, such as a drone-type AV, is provided a forward input whilealready moving in a forward direction. Accordingly, the frictionlessvehicle 101-1 travels in a forward direction along a trajectory 201-1.Since the frictionless vehicle 101-1 is already moving in a forwarddirection, it could also travel along trajectory 201-1 even without aforward input.

FIG. 2B shows a scenario in which a frictionless vehicle 101-2 beginswith a forward momentum and is provided with an input to rotate right.The frictionless vehicle 101-2 is shown to rotate toward the right as aresult of, for example, a yaw input to rotate right. However, thetrajectory 200-2 associated with the frictionless vehicle 101-2 does notcurve to the right. Instead, the trajectory 200-2 remains in a forwarddirection. Once the frictionless vehicle 101-2 begins rotating towardthe right, its momentum vector and its direction vector are no longeraligned. For example, the frictionless vehicle 101-2 is shown to befacing toward the right while its momentum vector is directed forwardthroughout its trajectory.

FIG. 2C shows a scenario in which a frictionless vehicle 101-2 beginstraveling along trajectory 200-3 with a forward momentum. Thefrictionless vehicle 101-3 is then provided a rotate right input and aforward input. As a result, the frictionless vehicle 101-3 experiences aclockwise rotation as well as an acceleration toward the right. Thefrictionless vehicle 101-3 thus travels along a trajectory that curvestoward the right. Any rightward momentum depends upon the frictionlessvehicle 101-3 first rotating clockwise before accelerating forward inthe rightward direction. As a result, the frictionless vehicle 101-3 hasa momentum vector that is not aligned with its direction vector. Forexample, at almost all points along trajectory 200-3, the frictionlessvehicle 101-3 has a direction vector that is pointed toward the right toa greater magnitude than its momentum vector.

FIG. 2D shows a scenario in which a frictionless vehicle 101-4 beginstraveling along trajectory 200-4 with a forward momentum. Thefrictionless vehicle 101-4 is then provided with a “rotate right” and a“roll right” input. In some embodiments, the “rotate right” and the“roll right” inputs are provided simultaneously throughout it's thetrajectory 200-4. The resulting trajectory 200-4 is shown therefore tocurve to the right, similar to trajectory 200-3. However, unlike in FIG.2C, the frictionless vehicle 101-4 is shown to maintain a momentumvector that is aligned with its direction vector throughout trajectory200-4. For example, when the frictionless vehicle 101-4 is caused toroll right in simultaneity with its rotating right, the frictionlessvehicle 101-4 experiences a rightward acceleration such that itstrajectory 200-4 curves to the right. The simultaneous rolling right ofthe frictionless vehicle 101-4 along with its rotating right causes themomentum vector of the frictionless vehicle 101-4 to be continuallyaligned with its direction vector. That is, for example, frictionlessvehicle 101-4 of FIG. 2D is consistently facing in the same directionthat it travels (e.g., it's momentum vector is aligned with itsdirection vector).

Embodiments described herein are for system and methods that enable africtionless vehicle such as a drone-type AV to maintain alignment ofthe vehicle's momentum vector with its direction vector. In certainembodiments, such alignment is achieved through a process of momentumalignment correction (MAC). MAC corrects or adjusts the momentumdirectionality of an AV such that its momentum vectors are consistentlythe same or close to same as the direction vector of the AV. In someembodiments, MAC is enabled to consistently maintain such an alignmentto within about 0.01° to about 45°, or about 0.1° to about 10°, or about0.5° to about 5°. An AV having MAC as described herein is thereforeenabled to have turning characteristics such that the AV consistentlytravels in a direction that corresponds to a direction it faces. Forexample, an operator of such an AV with MAC will find that the AVconsistently moves in the same or similar direction that the operatordirects the AV. As will be discussed in more detail below, MAC enablesthe AV to be operated and turned with a single axis of turning input asopposed to requiring an input for rotation and a simultaneous input forroll.

FIGS. 3A-3B show conceptual illustrations how a frictionless vehiclebehaves with and without momentum alignment correction, according oneembodiment. In FIG. 3A, turning characteristics of an AV without MAC areshown. When the AV is moving in a forward direction prior to a turn, itsmomentum vector faces in the same direction as the vehicle'sorientation. After the AV is rotated toward the right, the actualmomentum of the AV continues to be directed forward while the vehicle isdirected toward the right. The desired momentum corresponds to thevehicles orientation. As a result, the actual momentum does not alignwith either of the vehicle orientation or the desired momentum after theturn.

In contrast, FIG. 3B shows the certain turning characteristics of an AVwith methods and system of MAC described herein. In particular, the AVis shown to consistently have an actual momentum that corresponds toboth the desired momentum and the vehicle orientation throughout a turn.As a result, an AV with MAC will enable the AV to consistently corrector adjust the directionality of its momentum to match that of itsorientation. Thus, the MAC-enabled AV will turn such that the actualmomentum will be similar to a desired momentum.

FIG. 4 shows a conceptual illustration how an aerial vehicle navigates aturn with momentum alignment correction (MAC) in response to a singleaxis turning input, according to one embodiment. According to someembodiments, a single axis turning input refers to a mode of operatorinput that involves mechanical input along a single radial, rotational,tilt, or linear axis. For example, a single axis turning input mayinclude a steering wheel of an automobile, a handlebar of a bicycle ormotorcycle, a joystick when tilted along a linear axis, or any otherturning input mechanism that is manipulated along or around a singleaxis.

In the embodiment shown in FIG. 4 , an AV 400 is shown to be travelingin a forward direction. The AV 400 is shown to have a direction 402 anda momentum 404 that is also in the forward direction. Also shown in FIG.4 is a single axis turning input includes handle bar that receives aturning input 406 for turning toward the right. In response to theturning input 406, the AV 400′ is shown to have a direction 402′ thatpoints toward the right. The AV 400′ is also shown to have a momentum404′ that is pointed in the same direction as direction 402′ as a resultof momentum alignment correction. As will be discussed in more detailbelow, MAC is able to achieve alignment between momentum 404′ anddirection 402′ due to a specific mapping process by that is implementedby a flight computer or a module therein of the AV 400′. Briefly,however, the MAC module of the flight computer maps the turning input406 into signals that are distributed to various motors of the AV 400′.The mapping of the turning input 406 cause the AV 400′ to rotate in ayaw axis to the right and to tilt in the roll axis also to the right.The rotation in the yaw axis and the tilt in the roll axis are performedsimultaneously by the MAC and causes the momentum 404′ to be alignedwith the direction 402′ of the AV 400′ during the portion of the turnshown in FIG. 4 .

The MAC continues to correct or adjust the momentum 404″ such that itmatches direction 402″ of AV 400″ at a more advanced stage of thetrajectory 401. It is contemplated that as the turn continues intrajectory 401, the MAC will continue to ensure that momentum of the AV400 is directed in the same direction that the AV 400 is pointed toward.While the AV 400 will generally have a momentum 404 that is aligned withits direction 402, it is noted that at certain stages or portions of theturn that the degree of alignment may not be consistent. For example,the MAC may be configured to make certain adjustments during a turn inwhich the momentum 404 of the AV 400 is as aligned with its direction402 because certain adjustments or corrections in momentum 404 may causethe momentum 404 to momentarily not be as aligned with direction 402.

In some embodiments, it is contemplated that MAC may be switched on andoff. For example, when MAC is switched off, then the aerial vehicle 400may not turn in the manner shown in FIG. 4 with the momentum vector ofthe aerial vehicle aligned with its orientation vector (e.g., directionthe aerial vehicle faces). It is further envisioned that if MAC isswitched on when the aerial vehicle is not in a state of alignment, thenthe MAC processes carried out by the aerial vehicle will then beconfigured to achieve a state of alignment.

FIG. 5A shows a hoverbike 500 embodiment of a drone-type aerial vehiclethat may be implemented with the methods and systems of momentumalignment correction (MAC) described herein. The hoverbike 500 includesa main body 501, a seat 502 for an operator to sit, foot pegs 514 for anoperator to place their feet, a control panel 504 for interfacing withvarious parameters of the hoverbike 500, a handlebar 506 for controllingthe hoverbike 500 and for causing the hoverbike 500 to make turns. Thehandlebar 506 is a single axis turning mechanism that receivesmechanical input along a single rotational axis, in some embodiments.For example, the handlebar 506 is capable be manipulated to turn to theright or turn to the left according to input directionality 512. Inputdirectionality 512 of handlebar 506 shows the handlebar 506 can at leastbe rotated to the right and to the left, similar to, for example, ahandlebar on a bicycle or a motorcycle, according to some embodiments.

As will be discussed in more detail below, the rotational input providedto the handlebar 506 to turn toward the right or left is an input causesthe hoverbike 500 to experience a change in yaw that is simultaneouswith a change in roll in circumstances and in some embodiments, in otherembodiments, the handlebar 506 may have additional degrees of freedom,for example, that enable the handle bar 506 to be tilted forward orbackward, or side to side, to provide some other additionalflight-related input to the hoverbike 500. In some embodiments, atilting of the handlebar 506 forward may cause the hoverbike 500 todecrease its altitude, whereas titling the handlebar 506 backwardscauses an increase in the altitude in the hoverbike 500.

The hoverbike 500 of FIG. 5A also includes four motors 516 a-516 d thatdrive four propellers 518 a-518 d. The motors 516 a-516 d and propellers518 a-518 d provide lift to the hoverbike 500 as well as propulsion invarious directions. In some embodiments, a unit of a propeller and acorresponding motor may be referred to a propulsion unit. Although thehoverbike 500 embodiment is shown to include four propellers and fourmotors, it will be understood that other embodiments may include adifferent number of propellers and motors, and that such embodiments donot depart from the spirit and scope of the present embodiments. Forexample, it is envisioned that various embodiments may include between3-100 propulsion units, or between 4-64 propulsion units, or between4-16 propulsion units.

The handlebar 506 of the hoverbike 500 embodiment of FIG. 5A is alsoshown to include grips 508 a and 508 b, as well as a brake lever 510.The grips 508 a and 508 b may be stationary grips in some embodiments.In other embodiments, one or both of grips 508 a and 508 b may beconfigured to receive a rotational input similar motorcycle or scootergrip. The rotational input may be operable to control a forward momentumor speed of the hoverbike 500. In some embodiments, the hoverbike 500may be such that the right hand grip 508 b is configured to receive arotational input that maps to forward propulsion of the hoverbike 500,similar to a motorcycle or scooter. In various embodiments, the brakelever 510 may receive a clasping input that causes the hoverbike 500 toslow down. For example, if the hoverbike 500 is traveling in a forwarddirection, the brake lever 510 may be operable to decrease the momentumof the hoverbike 500 in the forward direction. The brake lever 510 maybe responsive to an amount of force that is applied to it such that theamount of braking force desired can be modulated via the brake lever510.

A flight computer (not shown) receives inputs from, for example, thehandlebar 506 being rotated left or right for turning, the grip 508 bbeing rotated for acceleration, and the brake lever 510 fordeceleration. The flight computer maps each of these inputs to thepropulsion units including motors 516 a-516 d and propellers 518 a-518d, as well as electronic speed controllers (ESCs), for causing thehoverbike 500 to behave in a desired manner. The flight computer (notshown) will include a module that is implemented as software, hardware,or firmware, which implements the processes associated with momentumalignment. As a result, the flight characteristics of the hoverbike 500will be such that its momentum (e.g., the direction the hoverbike 500travels) matches a directionality of the orientation of the hover bike500 (e.g., the direction the hoverbike 500 faces).

FIG. 5B shows a first person view of hoverbike 500, according to oneembodiment. In this view, a steering shaft 516 is shown be connected tothe handlebar 506 for translating left and right turning inputs from anoperator to a module (not shown) that transduces rotational inputreceived by the steering shaft 516 into electrical signals. Further,FIG. 5B shows that grip 508 b is configured to be rotated in thedirection 520 shown. As noted above, a rotation of grip 508 b may beoperable to cause acceleration in hoverbike 500. Moreover, brake 510 isshown movement in direction 518 for deceleration of the hoverbike 500,according to one embodiment. As a result, the hoverbike 500 has many ofthe same input configurations as a motorcycle, and is operable to beridden in a fashion that is similar to riding a bicycle or motorcycle.

FIG. 6 shows a schematic diagram of a hoverbike 500 embodiment and itspropulsion units 600-1 through 600-4. As noted above, a propulsion unitmay include at least a motor, a propeller, and in some embodiments anelectric speed controller (ESC) that controls the rotational speed of anassociated propeller by modulating power provided to the associatedmotor. The hoverbike 500 is shown to include four counter-rotatingpropulsion units. In the embodiment shown, for example, propulsion units600-1 and 600-4 are configured to rotate in a clockwise direction, whilepropulsion units 600-2 and 600-3 are configured to rotate in acounter-clockwise direction. In other embodiments, the hoverbike 500 mayinclude propulsions units 600-1 through 600-4 that rotate in theopposite direction as the configuration shown in the FIG. 6 . Forexample, in other embodiments, propulsion units 600-1 and 600-4 mayrotate in a counter-clockwise direction, while propulsion units 600-2and 600-3 rotate in a clockwise direction.

While certain embodiments described herein are made with reference toembodiments including four propellers, it will be appreciated that theprinciples of momentum alignment correction apply to aerial vehicleswith any number of propellers, as long as the various embodiments areenabled to control the roll and yaw of the aerial vehiclesimultaneously. Thus, various embodiments may be practiced with varyingnumbers of propellers without departing from the scope and spirit of thepresent disclosure. For the sake of clarity, however, FIGS. 7-12B andFIGS. 13A and 13B describe implementations of momentum alignmentcorrection using four propellers.

FIG. 7 shows an aerial vehicle navigating a turn that is in-progresswith momentum alignment correction. The aerial vehicle is travelingforward with some momentum in the forward direction before receiving aturn input 700, for example, from an operator. The turn input 700 iscontemplated to be input via a single axis steering input such as asteering wheel, a handlebar, joystick, or the like. The operator may betraveling with or on the aerial vehicle in some embodiments, or theoperator could be remote to the aerial vehicle in other embodiments. Theturn input 700 increases from 0 arbitrary units (e.g., no turn inputprior to the turn) to about 6.2 arbitrary units over a span of 4 unitsof time (e.g., 4 seconds) between t=0 and t=4. The turn input 700remains virtually consistent at 6.2 arbitrary units between about t=4 toabout t=10. As a result, the aerial vehicle receives a turn input thatincreases to a desired magnitude that then stays at the desiredmagnitude for some time.

The units of time, for example, during the period of t=0 to t=10 is alsodescribed in arbitrary units. It is envisioned, however, that the periodof t=0 through t=10 in which turning occurs (e.g., in FIGS. 7-12B and13A and 13B) may represent a period of roughly between about 0.2 secondsto about 30 seconds, or between about 1 second and about 10 seconds, orbetween about 2 seconds and about 5 seconds.

FIG. 7 shows the yaw 702, roll 704, and pitch 706 associated with theaerial vehicle during the period t=0 to t=10 in response to the turninput 700. For example, the yaw 702 of the aerial vehicle is shown toincrease non-linearly for about 4 seconds before increasing at a linearrate for the remainder of the turn. As a result, the aerial vehiclerotates at a consistent angular velocity after about t=4. Also inresponse to the turn input 700, the aerial vehicle experiences a roll704 that increases from 0° to about 10°, at which point the roll remainsroughly steady. The roll 704 experienced by the aerial vehicle causes itto change the momentum to the right by providing the aerial vehicle witha force toward the right. It should be noted that the initial change inroll 704 may exceed the initial change in yaw 702 towards the beginningof the turning process. Also, pitch 706 is shown to remain at or near 0°because no acceleration input is provided.

The roll 704 experienced by the aerial vehicle is caused by the turninput via a momentum alignment correction process. In the embodimentshown, for example, there is no external roll input. The resulting roll704 is automatically produced as a result of the momentum alignmentcorrection process derived from the turn input 700. As a result, theaerial vehicle is configured to convert the turn input 700 into both theillustrated change in yaw 702, as well as the change in roll 704 (e.g.,without an external roll input). The roll 704 produced by the momentumalignment correction process is configured to introduce a transverseforce that aligns the aerial vehicle's momentum with its degree ofrotation. For example, at t=4, the aerial vehicle has rotated (e.g., inthe yaw axis) roughly 18°. Due to the roll 704 of the aerial vehicle,the momentum of the aerial vehicle should also have a directionalitythat is roughly 18°. At t=8, for example, the aerial vehicle is shown tohave been rotated about 42°. Likewise, at t=8, the momentum of theaerial vehicle should also have a directionality of about 42°.

Generally speaking, the degree of roll 704 is roughly proportional tothe change in yaw 702. The following relationship may be used to expressthe general relationship between the change yaw 702 (e.g., angularvelocity) and the roll for aerial vehicles using momentum alignmentcorrection processes to align the directionality of the momentum of theaerial vehicle with its yaw:

$\begin{matrix}{\frac{d({yaw})}{dt} \propto {roll}} & (1)\end{matrix}$

For example, since the change in yaw 702 between t=6 and t=10 is roughlyconstant, the magnitude of the roll 704 during the same period is alsoroughly constant. If the change in yaw 702 is not constant over a periodof time, then the magnitude of roll 704 may also not be constant. Forexample, when there is an acceleration in yaw 702 (e.g., between t=0 andt=4), there a corresponding increase in roll 704.

FIG. 7 shows the power outputs of propulsion units 600-1 through 600-4,using the configuration of the hoverbike 500 as an example embodiment.For illustrative purposes, the effect of drag is not incorporated intothe diagrams. Propulsion unit 600-1 is disposed at the front left of theaerial vehicle, propulsion unit 600-2 at the front right, propulsionunit 600-3 at the rear left and propulsion unit 600-4 at the rear right.In the embodiment shown, propulsion units 600-1 and 600-4 rotateclockwise while propulsion units 600-2 and 600-3 rotatecounter-clockwise. The total value of power supplied counter-clockwiserotating propulsion units 600-2 and 600-3 is shown to be greater thantotal value of power supplied to the clockwise rotating propulsion units600-1 and 600-4. As a result, the aerial vehicle experiences a nettorque in the clockwise direction. The net torque in the clockwisedirection causes the aerial vehicle to rotate.

The net difference between the power supplied to the counter-clockwiserotating propulsion units 600-2 and 600-3 and the clockwise rotatingpropulsion units 600-1 and 600-4, and hence the magnitude of the netclockwise torque supplied to the aerial vehicle is shown to reach amaximum at roughly t=3. At time t=3, the aerial vehicle experiences itsgreatest angular acceleration, which is illustrated by yaw 703. Aftert=3, the net clockwise torque supplied to the aerial vehicle decreasesuntil it is almost negligible at around t=5. Although there is no longera net torque on the aerial vehicle, the aerial vehicle continues torotate (e.g., assuming that there are no drag forces) after t=5 at aconstant angular velocity, as shown by yaw 702.

Additionally, there is a difference between the total value of powersupplied to the left-hand side, or port propulsion units 600-1 and 600-3and the right-hand side, or starboard propulsion units 600-2 and 600-4.The result is a net torque on the aerial vehicle that causes roll 704that is toward the right. It should be noted that the aerial vehicleexperiences both a net torque in the yaw axis and the roll axis insynchrony as a result of turning input that is received from, forexample, a single axis steering input device. That is, for example, thechange in yaw 702 and change in roll 704 is produced as an automatic andsynchronized response to a turning input that is associated with asingle axis, a single dimension, or a single degree of freedom. Thesynchronized yaw and roll response caused by the turning input isenabled by momentum alignment correction processes, and results in thedirectionality of the momentum of the aerial vehicle being aligned withthe direction of the aerial vehicle throughout the turn shown in FIG. 7.

It should be appreciated that pitch 706 is shown to remain at 0° becausethe simulations provided in FIG. 7 assume a lack of drag for the sake ofillustration. In practice, there may indeed be a pitch command toaccelerate the aerial vehicle to counteract the effects of drag.

FIG. 8 shows a completed 33.3° turn by an aerial vehicle using momentumalignment correction at a relatively lower speed (e.g., as compared tothe same aerial vehicle completing a 33.3° turn at a higher speed). Forillustrative purposes, the diagrams shower ire FIG. 8 assume that nodrag forces are experienced by the aerial vehicle. Similar to FIG. 7 ,the aerial vehicle is shown to be traveling in a forward direction(e.g., in a direction of 0°) before receiving a turn input. The turninput 800 may be produced by a single axis steering mechanism such as asteering wheel, a handle bar, joystick, or the like. The turn input 800is shown to increase from 0 arbitrary units between t=0 to about t=4.5,reach a maximum at around t=4.5, and decrease to about 0 arbitrary unitsat around t=9. Such a turn input may be representative of a “completed”right turn in which the operator desires a to produce a certain degreeof turn and then terminate the turn (e.g., to return to going straightforward).

Accordingly, yaw 802, roll 804, and pitch 806 associated with the aerialvehicle throughout the completed turn are shown to result from the turninput 800. Similar to in FIG. 7 yaw 802 is shown to increase nonlinearlyat the outset of the turn, for example, between about t=0 and about t=4.This nonlinear increase in yaw 802 is in response to the increasingmagnitude of the turn input 800 and represents an angular acceleration.At about t=4.5, the aerial vehicle reaches a maximum rotationalvelocity, which corresponds roughly to the time in which the turn input800 reaches a maximum. In response to the decreasing turn input 800between about t=4.5 and about t=9, the rate of rate of increase of yaw802 decreases until at about t=9, yaw 802 reaches and remains at about33.3°.

Also in response to the turn input 800, roll 804 is shown increasebetween t=0 and t=4.5. At t=4.5, a maximum roll is reached at about 5°,and between about t=4.5 and about t=9, roll 804 is shown to decrease. Atabout t=9, roll is shown to be 0°. As noted above, momentum alignmentcorrection processes ensure that the aerial vehicle's momentum vector isaligned with its direction vector throughout the 33.3° turn. To achievesuch an alignment, the roll 804 is shown to increase simultaneously withthe increase to the change in yaw 802 at the outset of the turn in orderto provide a transversal momentum component to the aerial vehicle. Forexample, if the aerial vehicle has a yaw of 10°, then a roll componentmay provide a thrust that is transverse to 10°, for example, 100°. Asthe aerial vehicle continues to change in yaw, so will the direction offorce or thrust that the roll component provides.

As noted above, one way to execute momentum alignment control is toproduce a roll component that is proportional to the angular velocity ofthe aerial vehicle. That is, for example, a sharper turn (e.g., higherangular velocity) requires a larger roll component than a gentler turn(e.g., lower angular velocity). As a result, when angular velocity is ata maximum at t=4.5, the roll 804 reaches a maximum as well. And whenangular velocity is at 0, the roll 804 also has a value of 0°. Moreover,if there is an exponential change in yaw, there may also be anexponential change in roll.

FIG. 8 also shows the power that is supplied to propulsion units 600-1through 600-4 for the duration of the completed turn. Similar to FIG. 7, the difference in output between counter-clockwise rotatingpropulsions units 600-2 and 600-3 and clockwise rotating propulsionunits 600-1 and 600-4 results in a net clockwise torque on the aerialvehicle. The net clockwise torque causes the illustrated change in yaw802 in the clockwise direction between about t=0 and about t=5. Aftert=5, there is a net counter-clockwise torque that decelerates theangular velocity of the aerial vehicle until the angular velocitydecreases to zero after “completing” the turn.

Likewise, similar to FIG. 7 , the total value of power being output tothe port propulsion units 600-1 and 600-3 is higher than that of thestarboard propulsion units 600-2 and 600-4 between t=0 and t=5, whichcauses increasing roll 804 shown in FIG. 8. After about t=5, the totalpower output of the starboard propulsion units 600-2 and 600-4 becomegreater than that of the port propulsion units 600-1 and 600-3. As aresult, the roll 804 of the aerial vehicle begins to decrease. Thus,during about t=5 through t=10, the aerial vehicle begins to straightenback out to complete the turn.

FIG. 9 shows an aerial vehicle completing a 33.3° turn at a greaterspeed than the aerial vehicle of FIG. 8 . The turn input 900 is similarto the turn input 800 of FIG. 8 , which produces a yaw 902 that issimilar to the yaw 802 of FIG. 8 . However, unlike in FIG. 8 , the roll904 is shown to increase much faster and reach a maximum that is almosttwice the magnitude of the maximum roll 804 of FIG. 8 . Thus, the roll904 is function of both speed and of angular velocity of the aerialvehicle. In the embodiment shown, the roll 904 is shown to increase at agreater rate than yaw between about t=0 and t=2. The roll 904 isrequired to increase faster and to a higher maximum at relatively higherspeeds because a greater transversal force is required to change thedirection of momentum for an aerial vehicle that is traveling fasterthan one traveling slower in an initial direction. Thus, the rollcomponent or the amount of transversal momentum generated by the rollcomponent may be proportional to momentum of the aerial vehicle inaddition to being proportion to its angular velocity.

The rotor outputs of propulsion units 600-1 through 600-4 reflect theincreased roll component required to maintain the alignment between thedirectionality of the momentum and the direction of the aerial vehicle.It is noted that the power curves for the propulsion units 600-1 and600-2 have qualitatively swapped places in FIG. 9 as compared to FIG. 8due to the increased momentum associated with the aerial vehicle goinginto the turn.

FIG. 10 illustrates a completed turn of an aerial vehicle in response toa varying turn input using momentum alignment correction processes. Thetype of turn input 1000 and the resulting turn may be a result of anoperator who performs one or more corrections during the course of aturn, for example. The flight path 1001 is shown to be not as smooth asflight path 1003, the latter of which describing a trajectory the aerialvehicle would take were it not for the turn input correction betweenabout t=3 and about t=5.

The aerial vehicle is traveling forward with some momentum when a sharpturn input is received. The turn input reaches a maximum at around t=3,after which the pilot corrects and reduces the magnitude of the turnbetween about t=3 and about t=4. This may be the case when the pilotturns too aggressively initially and produces a turn output that isgreater than what is desired and reduces the turn input in response.While the turn input 1000 is reduced during this period, it does notdecrease to 0 turn input, and so the aerial vehicle remains turningthroughout the duration shown (e.g., t=0 to t=10). At around t=4, theturn input 1000 is increased again before the turn is terminated and theturn input is reduced to 0.

FIG. 10 shows the yaw 1002, roll 1004, and pitch 1006 that is producedby momentum alignment correction processes in response to the turninput. Because the forward momentum of the aerial vehicle is relativelyhigh prior to and during the turn, the roll 1004 is shown to increase ata higher rate than the yaw 1002 between about t=0 and t=2. Roll 1004 isshown to reach a maximum at around t=3, which corresponds to the timepoint at which the turn input 1000 is maximal. Roll 1004 decreasesbetween about t=3 and about t=4 due to the reduced magnitude of the turninput 1000 during the same period. Roll 1004 increases once againbetween about t=4 and t=5 in response to the increased turn input 1000during the same period. After t=5, the roll 1004 decreases until theturn input 1000 reaches zero and when the angular velocity of the aerialvehicle no longer changes.

It should be noted that while the turn input 1000 is shown to cause achange in the roll 1004 and the yaw 1002 characteristics of the aerialvehicle, the roll 1004 component is not an external or manual input madeby the pilot. Instead, the roll 1004 component is mapped from the turninput 1000, which may be from a single axis turning input. The creationof the roll 1004 component from a turn input 1000 that is related torotation or change in yaw is accomplished by momentum alignmentcorrection. Without momentum alignment correction, a turn input willcreate a change only in yaw, and, as a result, no change in roll will beproduced from the turn input. As a further result, the direction of theaerial vehicle's momentum will not be aligned with the direction theaerial vehicle is facing. One of the technological advantages ofmomentum alignment correction is ensuring the aerial vehicle's directionof momentum is consistently aligned with the direction it is facing.FIG. 10 demonstrates the capabilities of momentum alignment correctionin maintaining such an alignment even when the turn input is not smooth.Embodiments described herein are enabled by momentum alignmentcorrection to maintain an aerial vehicle's momentum vector with itsdirection vector for various types of turns. The rotor output for eachof the propulsion units 600-1 to 600-4 are also shown in FIG. 10 .

Each of the power curves for propulsion units 600-1 through 600-4 areshown to cross the power=25 line several times. For example, at aroundt=3.5, each of the power curves are shown to cross the power=25 line,which happens again at about t=4.5 and t=5.5. The power curves reversein the first instance at t=3.5 due to the decreased pilot turn inputshown at around t=3, which requires that the aerial vehicle's yawmomentum be slowed down. At around t=4, the pilot's turn input is shownease again, which causes the yaw momentum of the aerial vehicle to besped back up. As a result, at about t=4.5, each of the power curves forpropulsion units 600-1 through 600-4 again cross the power=25 line suchthat the vehicle's angular momentum in the yaw axis is again increasedfor a sharper turning radius. The power curves of propulsion units 600-1through 600-4 again cross power=25 line at about t=5.5 in response tothe decreased pilot turn input at around t=5.

FIGS. 11A and 11B show how a flight computer in communication with orincluding a momentum correction module is able to map various turninputs to power output signals that are sent to propulsion units 600-1to 600-4. FIG. 11A, for example, shows an embodiment of an aerialvehicle that receives turn input 1100 and maps, in real time or nearreal time by a momentum alignment correction module, to power signalsthat are supplied to the propulsion units 600-1 through 600-4. The turninput is shown to increase between t=0 to about t=4.5, after which pointthe turn remains steady. Thus, the turn input 1100 may represent asustained turn. For example, a sustained turn such as that shown in FIG.11A may result in the aerial vehicle turning perpetually such that itfollows a circular trajectory. FIG. 11B shows an embodiment of how aturn input 1102 for a completed turn is mapped by a momentum alignmentcorrection module to propulsion units 600-1 to 600-4.

FIGS. 12A and 12B show certain difference between the mapping processesprovided by the momentum alignment correction module for an aerialvehicle that is directed to complete a large (e.g., sharper turn) turnin FIG. 12A as compared to a similar aerial vehicle that is directed tocomplete a smaller (e.g., gentler turn). FIG. 12A shows a turn input1200 that is sharper than the turn input 1202 of FIG. 12B. Generallyspeaking, sharper turns (e.g., turn input 1200) require a greaterangular velocity, and therefore a greater net torque on the aerialvehicle. Due to the greater angular velocity required for sharper turns,a greater roll component is also required in order to provide a greateramount of transversal propulsion to “correct” the momentum of the aerialvehicle such that the directionality of the momentum aligns with thedirection the aerial vehicle is facing in real time. When an aerialvehicle turns faster, a greater magnitude of roll is generally requiredto produce the change in momentum directionality that is simultaneous ornear simultaneous to the change in the direction the aerial vehicleexperiences. In some embodiments, there may be a lag between matching orcorrecting an aerial vehicle's momentum vector with its directionvector. It is envisioned that momentum alignment correction is to beable to correct an aerial vehicle's momentum vector with its directionvector within about 0 seconds (e.g., real time) to about 2 seconds, orabout 0.01 seconds and about 1 second, or about 0.1 seconds and 0.5seconds. In some embodiments, the “time to alignment” (e.g., the time ittakes to align an aerial vehicle's momentum vector with its directionvector) small enough such that the operator feels as though alignment isachieved in real time. It is contemplated that as long a time toalignment is achieved within about half of a second or less, then theoperator may not be able to distinguish the time to alignment with realtime alignment. In other embodiments, the time to alignment may beconfigured to less than 0.5 seconds.

In various embodiments, momentum alignment correction processes andmodules are also enabled to preemptively change an aerial vehicle'smomentum vector in response to a predicted change in directionalityvector. That is, for example, an aerial vehicle turning clockwise andpredicted to continue to turn clockwise may be provided with a traversalthrust that preemptively increases the aerial vehicles lateral momentumsuch that the momentum vector changes ahead of the change indirectionality vector.

FIG. 13A shows an overall flow of an embodiment for executing a turnusing momentum alignment correction to maintain an aerial vehicle'smomentum vector with its directionality vector during the turn.Operation 1300 serves to determine the current momentum of the vehicle.In various embodiments, operation 1300 may obtain the current momentumof the vehicle based on accelerometers, GPS tracking, motion detectors,radar, infrared sensors, magnetic sensors, among other ways to obtain avehicle's current momentum. By determining the vehicle's momentum,operation 1300 contemplated to determine both the magnitude and thedirection of the vehicle's momentum. Generally, operation 1300 will alsorequire a measurement for the mass of the vehicle to determine thecurrent momentum. In some embodiments, it is envisioned that the mass ofthe vehicle may be estimated from overall power consumption of thevehicle on takeoff after adjusting for altitude and temperature. Inother embodiments, the mass of the vehicle may also be determined fromload cells or from a user-inputted value. In yet other embodiments, themass could be determined or inferred in flight by measuring the amountcorrection required during the first turn the vehicle makes from a setof assumptions or default values. Assume, for the sake of example, thatthe mass of the vehicle is 100 kg and that it is traveling 1meter/second in the 0° direction. Operation 1300 is thus able tocalculate its momentum to be 100 kg×m/s.

According to the embodiment of FIG. 13A, operation 1305 serves todetermine a current direction vector of the vehicle (e.g., orientation).That is, operation 1305 serves to detect which way the vehicle isfacing, since it may be the case that the (aerial) vehicle does not facethe same direction that it travels. If it is assumed that the aerialvehicle does travel in the same direction that it faces, then followingthe example provided in the preceding paragraph, operation 1305 maydetermine that the vehicle is facing in the 0° direction.

If, on the other hand, the momentum is not aligned with the direction ofthe vehicle prior to the turn, an addition momentum correction componentmay be computed in operation 1330 to adjust the roll component needed to(a) correct for the detected difference in the momentum vector and thedirection vector as calculated by operations 1300 and 1305,respectively, as well as to (b) implement a momentum alignmentcorrection component as calculated by operation 1320.

At operation 1310, the method receives a turn input, for example, froman operator who is riding or driving the vehicle. The turn inputreceived in operation 1310 may be transduced from a mechanical changein, for example, a steering mechanism such as a steering wheel,handlebars, joystick, etc., into an electric signal. In certainembodiments, the turning input received by operation 1310 is from asingle axis turning or steering input mechanism. As noted above, asingle axis turning or steering input mechanism is operable as an inputdevice that provides input in one-dimensional space. For example, asteering wheel or handle bars maybe characterized as single axis turningor steering mechanisms because the input produced by such inputmechanisms is confined to one dimensional space.

According to the embodiment shown in FIG. 13A, operation 1320 determinesa change in yaw based on the turning input. For example, if the vehicleis traveling at 0° and receives a certain turn input, operation 1320determine that change in yaw that such a turn input will produce. Forexample, a clockwise turn input of a particular magnitude may result ina change in yaw, or angular velocity of, for example, 10°/second. Thus,the vehicle is able to complete a 90° turn in about 9 seconds.

In operation 1330, the method includes calculating by a momentumalignment control module, a momentum correction component for thedetermine change in yaw such that the change in momentum vector matchesthe determined change in yaw. For example, the momentum alignmentcorrection module in operation 1330 may calculate how much change inmomentum is required to change the momentum vector at a rate of10°/second in order to align the momentum vector with the change in yaw.To effect a change in the momentum vector at a rate of 10°/second (e.g.,to match the change in the direction vector), operation 1330 maydetermine that the vehicle is to produce a transversal thrust or forceof about 17.36 kg×m/s². This thrust, propulsion, or force in thetransverse direction (e.g., to the right of forward) may be referred tothe momentum correction component, since it refers to a component ofthrust that changes the directionality of the momentum vector of thevehicle.

If it is the case that the momentum vector and the direction vector arenot aligned prior to receiving the turning input at operation 1310,operation 1330 may also calculate an additional momentum correctioncomponent that is to be implemented to correct for the initialnon-alignment. As a result, operation 1310 may produce a momentumcorrection component that corrects for both the initial non-alignment aswell as the non-alignment would be created by the turn input.

In operation 1340, the method includes determining a roll componentbased on the calculated momentum correction component of 17.36 kg×m/s².For example, operation 1340 will determine to what degree the vehicleshould roll to right to produce the momentum correction component.Depending on various parameters, operation 1340 may determine that aroll component should be an 8.8° roll to the right. Generally, operation1340 will determine an amount of roll that should be executed withoutaffecting the thrust of the vehicle in the direction of gravity. Inoperation 1350, the method includes executing the turn based on thedetermine change in yaw as communicated by the turning input received inoperation 1310 and based on the roll component determined in operation1340. Operation 1350 is therefore configured to control a distributionof power to the propulsion units such that the vehicle is caused toexperience a change in yaw at about 10°/second as well as a rollcomponent of about 8.8°. As a result, the momentum vector of the vehicleexperiences an angular change of 10°/second, which matches the vehicle'schange in yaw of 10°/second.

The resulting turn that is executed by the method of FIG. 13A is suchthat the vehicle's momentum vector is consistently aligned with itsdirectionality vector. From the operator's point of view, the vehicletravels in the same direction as it faces throughout the turn. For anoperator, the flight behavior and characteristics of a vehicle beingoperated in conjunction with the method shown in FIG. 13A is intuitivebecause the vehicle travels in the same direction that it faces, similarto the behavior of ground vehicles. Thus, the method represents animprovement to current aerial vehicles and control systems thereof. Forexample, when an aerial vehicle piloted by a human travels in adirection that it does not face (e.g., the vehicle travels in the 90°direction but faces the 0° direction), confusion and unwanted resultsmay occur. Embodiments contemplated here ensure that when an aerialvehicle faces a certain direction and has some momentum, the momentumwill continually be in the same direction that the vehicle faces. Otherembodiments contemplated here are enabled to control an aerial vehiclein a way that mimics how ground vehicles or friction-based vehicles arecontrolled. Namely, embodiments envisioned here mimic the groundvehicle's ability to align its momentum vector with its directionvector.

FIG. 13B illustrates an aerial vehicle 1301 and certain associatedcomponents of its flight computer 1300. The flight computer is shown toreceive pilot input 1302, which is processed by turning input sensormodule 1304. In certain embodiments, the pilot input 1302 is producedfrom a single axis turning input mechanism such as handlebars, ajoystick, or a steering wheel. Turning input sensor module 1304processes the raw pilot input 1302 signal into computer-readable signalsrelated to the directionality and the magnitude of the pilot input 1302.The computer-readable turning signals related to the pilot input 1302are processed by a vehicle yaw change detection module, which calculatesthe change in yaw that is to be produced by the pilot input 1302 in realtime or near real time. Propulsion unit power distribution module 1308calculates and maps the amount of power that should be delivered to eachof the four propulsion units to accomplish the calculated change in yaw,or however many propulsion units are included in various embodiments.

The momentum alignment correction module 1316 is shown to receive inputsfrom the turning input sensor module 1304, the vehicle yaw changedetection module 1306, the vehicle yaw, roll, and pitch detection module1318, the vehicle mass sensing module 1312, and the momentum detectionmodule 1314. The vehicle mass sensing module 1312 may communicate withsensors that physically interpret the mass of the aerial vehicle, or maycommunicate with sensors that infer the mass of the vehicle from powerconsumption sensors or feedback loops. Signals from each of thesesources are used to compute a momentum correction component that is tobe executed by the propulsion unit power distribution module 1308simultaneously to its executing the command received by the vehicle yawchange detection module 1306. More particularly, the momentum alignmentcorrection module 1316 receives information to the current state of thevehicle from the vehicle yaw, roll, and pitch detection module 1318, andthe current momentum of the vehicle from momentum detection module 1314.Additionally, the momentum alignment correction module obtains datarelated to the direction and magnitude of pilot input 1302 from thevehicle yaw change detection module 1306.

In the embodiment shown in FIG. 13B, the momentum alignment correctionmodule 1316 is configured to calculate, in real time, the momentumcorrection component needed to produce a change in the momentum vectorthat matches the change in yaw. The momentum correction component, oncecalculated, is converted into a roll component, which represents anamount of roll that is to be executed to achieve the momentum correctionneeded to change the direction of the momentum of the vehicle at a ratethat matches the change in yaw. The roll component calculated by themomentum alignment correction module 1316 is feed into the propulsionunit power distribution module 1308, which is responsible for combiningthe yaw command that is being received from the vehicle yaw changedetection module 1306 and the roll command being received from themomentum alignment correction module 1316 and calculating thedistribution of power that is to be sent to each of the propulsion unitsto achieve the received yaw command and roll command simultaneously. Thepropulsion unit power distribution module 1308, having calculated thedistribution of power required achieving the yaw and roll commandsimultaneously, signals to the electronic speed controllers of each ofthe propulsion units to draw power from a battery supply (not shown) orother power supply that is in accordance with the calculateddistribution of power.

It is noted that the components shown in flight computer 1300 and theprocesses they facilitate have been described sequentially for the sakeof clarity. However, it will be understood that the abovementionedprocesses are occurring over a period of time in real time. Thus, thepower distribution is a dynamical distribution. The yaw and rollcommands are also dynamic inputs that change in real time depending uponthe pilot input 1302, as well as external conditions.

FIG. 14 shows a method for making momentum correction to an aerialvehicle when it is detected that momentum is not aligned with theorientation of the aerial vehicle (e.g., the direction the aerialvehicle is facing). In operation 1440, the orientation of the aerialvehicle is detected, for example, by GPS system. For example, operation1440 may detect that the orientation of the aerial vehicle faces in the0° direction. In operation 1450, the method detects the momentum vectorof the aerial vehicle (e.g., the direction in which the vehicle istraveling). For example, operation 1450 may detect that the momentumvector of the aerial vehicle is directed in the 1° direction. Theorientation obtained in operation 1440 is then compared to the momentumvector data obtained in operation 1450 in operation 1460, which is alsooperable to calculate an amount of correction in a roll component tocompensate for the difference. If there is a difference, as there is inthe current example, the amount of roll correction is calculated andused as feedback to operation 1410, which detects the current momentumof the aerial vehicle. Additionally, it is contemplated that in somecircumstances for some embodiments that a pitch or yaw adjustment may becalculated by operation 1420 in order to cause the momentum vector ofthe aerial vehicle to be aligned with its direction vector.

Operation 1420 is configured to calculate a roll component necessary tomaintain alignment between the momentum vector with the orientation ofthe aerial vehicle based on the received turn input. However, when thereis a roll correction provided by operation 1460, operation 1420calculates a roll that is necessary to satisfy both the received turninput as well the additional roll correction. In some situations, theroll correction pray be additive to the calculated roll for the turninput if the momentum vector is “lagging behind” the orientation. As aresult, a greater roll command will allow the momentum vector of theaerial vehicle to “catch up” to the orientation. In other situations,the roll correction may be negative and subtract from the calculatedroll from the turn input, if, for example, the momentum vector hasovershot the orientation of the aerial vehicle. In any case, theembodiment shown is enabled to make on-the-fly adjustments to themomentum vector of the aerial vehicle to create an alignment between thevehicle's momentum vector with its orientation.

In certain other embodiments, the moment of inertia may also be detectedto determine the amount of angular force required execute respectivedesired roll commands and yaw commands. When the momentum of inertia ishigher, it will generally take a greater amount of angular force toeffect a desired roll command or a desired yaw command. Thus, in certainembodiments, the aerial vehicle may include one or more sensors fordetecting the momentum of inertia in the yaw, roll, and pitch axes,which can be used by the flight computer to execute various roll and yawcommands, in addition to pitch commands.

FIGS. 15A and 15B show embodiments that prevent an aerial vehicle fromrolling past a desirable magnitude or degree, hereinafter referred to asover-roll, for example, during a turn. In certain situations, over-rollmay not be desirable because it may cause a side of the aerial vehicle(e.g., the propellers) to become too close to the ground or otherobject. In other situations, over-roll may be problematic when theoperator is being tilted to one side more than would be desirable.

In FIG. 15A, an aerial vehicle implementing momentum alignment controlis given a yaw input that causes the aerial vehicle to turn. A steadymanual roll input 1502 is shown to occur during the period t=0 to t=10.Additionally, a roll command 1504 as generated by the momentum alignmentcontrol (MAC) of the aerial vehicle is also shown. The threshold 1508illustrates acceptable degrees of roll and unacceptable degrees of roll.Individually, neither of the manual roll input 1502 nor the MACgenerated roll command 1504 surpass the threshold 1508. However, when apilot commands both an external roll and a turning input, the combinedroll 1506 may be greater than what is an acceptable roll.

One way to prevent over-roll 1500 such as that shown in FIG. 15A is touse over-roll automatic correction 1501, as shown in FIG. 15B. Over-rollcorrection or prevention involves continually monitoring the combinedroll 1506′ by monitoring the manual roll input 1504′ and the MACgenerated roll command 1504′. When the combined roll 1506′ nears or ispredicted to surpass the threshold 1508, the flight computer of theaerial vehicle may limit the yaw input, for example, by mechanicallylimiting the magnitude in which a single axis turning device can beturned or manipulated. As a result, the combine roll 1506′ does notexceed threshold 1508. Alternatively, or additionally, the flightcomputer of the aerial vehicle may also limit the roll input so that thecombined roll 1506′ of the aerial vehicle does not exceed the threshold1508.

FIG. 16 shows a method for implementing over-roll correction orprevention in aerial vehicles such as those embodiments describedherein. In operations 1600-1620, the method includes receiving a turninput, detecting a current momentum of the aerial vehicle, andcalculating a roll necessary to maintain alignment of a momentum vectorof the aerial vehicle with its orientation. In operation 1630, themethod includes detecting a current roll as well as an external rollinput. Operation 1640 combines all roll values detected by operations1620 and 1630 to determine a combined roll value. If it found bydecision 1650 that the combine roll value is above a given threshold,then the method proceeds to operation 1670, which serves to limit theturn input and/or the roll input that an operator is able to produce. Ifinstead it is found that in decision 1650 that the combined roll valuedoes not exceed a given threshold, then the method proceeds to operation1660 does nothing to the limit the turn input.

For the sake of illustration, embodiments of flight characteristics,including yaw, pitch, roll, and rotor outputs have been purposefullyisolated from certain external forces that may act upon the embodimentsof aerial vehicles described herein such that the principles ofimplementing momentum alignment correction and over-roll correction maybe better illustrated. It will be appreciated, however, that additionalforces may act upon the aerial vehicle, and may therefore affect theillustrated yaw, pitch, roll, and rotor outputs shown in FIGS. 7-12B andFIGS. 13A and 13B. For example, forces caused by drag as well as forcescaused by a pilot have been intentionally suppressed in order to betterillustrate how principles of momentum alignment correction and over-rollcorrection should be implemented. In practice, however, it is notedthat, for example, a pitch adjustment may be needed in variousembodiments such that the aerial vehicle maintains speed or momentumthroughout the turn.

Additionally, a pilot may produce forces on the aerial vehicle such asby shifting her weight side to side as well as fore and aft. As aresult, the pilot may cause the center of gravity of the aerial vehicleto change. In addition to changing the center of gravity of the aerialvehicle, the pilot may also produce a torque on the vehicle. Forexample, in the hoverbike 500 embodiment shown in FIGS. 5A and 5B, apilot that leans to the left or right may also torque the hoverbike 500left or right (e.g., in the roll axis). Additionally, the pilot maytorque the hoverbike 500 in the yaw and pitch axes. It is thereforecontemplated that the flight computers used with embodiments describedhereinabove are enabled to compensate for external forces experienced bythe aerial vehicle.

Although the method operations were described in a specific order, itshould be understood that other housekeeping operations may be performedin between operations, or operations may be adjusted so that they occurat slightly different times or may be distributed in a system whichallows the occurrence of the processing operations at various intervalsassociated with the processing, as long as the processes of momentumalignment correction and over-roll correction are performed in thedesired way.

One or more embodiments can also be fabricated as computer readable codeon a computer readable medium. The computer readable medium is any datastorage device that can store data, which can be thereafter be read by acomputer system. Examples of the computer readable medium include harddrives, network attached storage (NAS), read-only memory, random-accessmemory, CD-ROMs, CD-Rs, CD-RWs, magnetic tapes and other optical andnon-optical data storage devices. The computer readable medium caninclude computer readable tangible medium distributed over anetwork-coupled computer system so that the computer readable code isstored and executed in a distributed fashion.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, it will be apparent thatcertain changes and modifications can be practiced within the scope ofthe appended claims. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the embodiments arenot to be limited to the details given herein, but may be modifiedwithin the scope and equivalents of the appended claims.

What is claimed is:
 1. A method for turning an aerial vehicle, themethod comprising: receiving, at the aerial vehicle, a turning input;detecting a momentum of the aerial vehicle; converting the turning inputinto a yaw command and a roll command based on the momentum; andexecuting, by the aerial vehicle, the yaw command and the roll commandin synchrony to cause the aerial vehicle to perform a turn.
 2. Themethod of claim 1, wherein a momentum vector of the aerial vehicle andan orientation vector of the aerial vehicle are aligned during the turn,the momentum vector is defined by a directionality associated with themomentum of the aerial vehicle and the orientation vector is defined bya direction the aerial vehicle is facing.
 3. The method of claim 2,wherein the momentum vector and the orientation vector are within 10° ofeach other when aligned.
 4. The method of claim 1, wherein saidconverting the turning input into the yaw command and the roll commandcomprises: calculating the yaw command based on the turning input;calculating a change in yaw based on the yaw command; and calculatingthe roll command based on the change in yaw and the momentum of theaerial vehicle.
 5. The method of claim 4, wherein said calculating theroll command further comprises: calculating a future momentum that willbe associated with the aerial vehicle in response to the turning input;and determining a transversal momentum component based the differencebetween the future momentum and the momentum of the aerial vehicle;wherein the roll command is further calculated based on the transversalmomentum component.
 6. The method of claim 4, wherein said calculatingthe roll command comprises: determining a momentum correction componentthat is operable to change a momentum vector of the aerial vehicle at asimilar angular rate to the change in yaw; and calculating a degree ofroll for achieving the momentum correction component, wherein the rollcommand is based the degree of roll calculated and the roll command isexecuted by a plurality of propeller units of the aerial vehicle.
 7. Themethod of claim 1, wherein said executing the yaw command and the rollcommand in synchrony comprises: initiating the roll command and theninitiating the yaw command.
 8. The method of claim 1, wherein theturning input is produced by a single axis steering device.
 9. Themethod of claim 8, wherein the single axis steering device includes asteering wheel, or a handlebar, or a joystick.
 10. The method of claim1, wherein the yaw command is operable to generate torque on the aerialvehicle via a plurality of propeller units of the aerial vehicle. 11.The method of claim 1, wherein the roll command is operable to generatea change in roll of the aerial vehicle via a plurality of propellerunits of the aerial vehicle.
 12. An aerial vehicle, comprising: one ormore sensors for determining a momentum of the aerial vehicle; a singleaxis turning device for receiving a turning input; a flight computerconfigured for converting the turning input into a yaw command and aroll command based on the momentum; and a plurality of propulsion unitsfor executing the yaw command and the roll command in synchrony to causethe aerial vehicle to perform a turn.
 13. The aerial vehicle of claim12, wherein the flight computer is configured to continually update theroll command based on the yaw command such that a momentum vector of theaerial vehicle and an orientation vector of the aerial vehicle are in astate of continual alignment during performance of the turn, wherein themomentum vector is defined by a directionality associated with themomentum of the aerial vehicle and the orientation vector is defined bya direction of the aerial vehicle is defined by a direction the aerialvehicle is facing.
 14. The aerial vehicle of claim 12, wherein saidconverting the turning input into the yaw command and the roll commandcomprises: calculating the yaw command based on the turning input;calculating a change in yaw based on the yaw command; and calculatingthe roll command based on the change in yaw and the momentum of theaerial vehicle.
 15. The aerial vehicle of claim 12, wherein saidcalculating the roll command further comprises: calculating a futuremomentum that will be associated with the aerial vehicle in response tothe turning input; and determining a transversal momentum componentbased the difference between the future momentum and the momentum of theaerial vehicle; wherein the roll command is further calculated based onthe transversal momentum component.
 16. The aerial vehicle of claim 12,wherein said calculating the roll command comprises: determining amomentum correction component that is operable to change a momentumvector of the aerial vehicle at a similar angular rate to the change inyaw; and calculating a degree of roll for achieving the momentumcorrection component, wherein the roll command is based the degree ofroll calculated.
 17. The aerial vehicle of claim 12, wherein the turninginput is a yaw input and wherein the roll command is generated by theflight computer automatically without an additional roll input.
 18. Themethod of claim 12, wherein the single axis steering device includes asteering wheel, or a handlebar, or a joystick.
 19. A non-transitorymachine-readable storage medium comprising a computer program, thecomputer program comprising a set of instructions for: receiving, at theaerial vehicle, a turning input; detecting a momentum of the aerialvehicle; converting the turning input into a yaw command and a rollcommand based on the momentum; and executing, by the aerial vehicle, theyaw command and the roll command in synchrony to cause the aerialvehicle to perform a turn.
 20. The non-transitory machine-readablestorage medium of claim 19, wherein said converting the turning inputinto the yaw command and the roll command comprises: calculating the yawcommand based on the turning input; calculating a change in yaw based onthe yaw command; and calculating the roll command based on the change inyaw and the momentum of the aerial vehicle.